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[Cerebrovascular Surgery Center]

Neurovascular Surgery
Brain Aneurysm & AVM Center

by Christopher S. Ogilvy, M.D.

Factors affecting management decisions | Management scheme | Figures | Other sources of information

A giant intracranial aneurysm is defined as one larger than 2.5 cm in diameter. Treatment of large (2-2.5 cm) and giant aneurysms has traditionally been associated with a higher morbidity and mortality than smaller lesions. Giant aneurysms are thought to represent about 5-8% of all intracranial aneurysms. Size does not influence the hemorrhage rate, and approximately 25% of patients present with subarachnoid hemorrhage. Seventy to seventy-five percent of patients with giant aneurysm present with mass effect, usually manifest by visual failure, cranial nerve dysfunction, hemiparesis, seizure or headache. Thrombosis and stroke due to blood clot formation within the aneurysm and subsequent distant embolus, occurs in some 2-5% of patients with giant aneurysms. Sixty percent of giant aneurysms occur on the internal carotid artery. An additional 10% occur in the anterior communicating artery region, with 10% occurring in the middle cerebral artery. Fifteen percent of these giant lesions occur at the top of the basilar artery, and approximately 5% arise from the vertebral artery.

Several different strategies are currently available to manage giant aneurysms. This stems from the fact that no single technique is effective in dealing with all giant aneurysms. Current treatment options for these lesions include direct surgical techniques, endovascular techniques, and combined approaches. Regarding surgery, the aneurysm can be attacked directly with clipping and resection of the mass lesion, or aneurysmorrhaphy with vessel reconstruction. Indirect surgical techniques include proximal occlusion and trapping of the aneurysm using clips or ligature above and below the lesion. Alternatively, if the patient is unable to tolerate occlusion of the parent vessel in relation to a giant aneurysm, an extracranial to intracranial bypass procedure can be performed with subsequent trapping or proximal occlusion of the vessel. This typically arises as an issue in internal carotid artery aneurysms. More recently, intracranial bypass procedures have been described for reconstruction of the carotid artery with saphenous vein grafts or aneurysm resection with middle cerebral artery reconstructions.

Endovascular techniques include balloon trapping with balloons placed intravascularly above and below the giant aneurysm. Proximal balloon occlusion is a useful and often used technique for giant internal carotid artery aneurysms, specifically those arising within the cavernous sinus. If the balloon occlusion is tolerated anywhere in the intracranial circuit, this technique can be useful if the balloon can be placed adjacent to the aneurysm. Balloon placement within the aneurysm was a technique which was associated with a significant morbidity and therefore has largely been replaced by coil embolization of giant lesions. Guglielmi detachable coils are another means of endovascular occlusion of giant intracranial aneurysms. While there are some concerns regarding reshaping of the coils once they are packed in giant aneurysms, and coil migration into thrombus which is present in giant aneurysms, this overall strategy may provide a means of treating carefully selected lesions.

Other treatment options for giant aneurysms include combined techniques. In this approach, a surgical procedure such as an intracranial to extracranial bypass can be performed prior to endovascular occlusion of the parent vessel. Alternatively, bypass techniques can be combined with endovascular trapping of certain giant aneurysms or intra-aneurysmal endovascular techniques.

Factors affecting decision

Careful consideration should be given prior to treatment of any giant aneurysm regarding specific anatomic features. It is well known that critical perforating vessels can arise from the aneurysm itself. In addition, parent vessels of origin may be included in the aneurysmal wall as the aneurysm grows over time. Consideration in direct surgical attack is that a thick, calcified wall may not accept an aneurysm clip. In this instance, aneurysmorrhaphy (opening of the aneurysm and removing intra-aneurysmal clot) may be necessary. If this is to be performed in an elderly patient, careful consideration of risk must be balanced against other available strategies to treat the aneurysm.

Several adjuncts have been developed to aid direct surgery for giant aneurysms. Techniques of cardiac arrest allow for a slack aneurysm which can be dissected from surrounding cerebral tissue. Temporary occlusion of the parent vessel can also allow decompression of the aneurysm.

Management scheme

Since 1989, at the MGH Aneurysm/AVM Center we have evaluated patients on a case by case basis to find treatment strategies using direct microsurgical clipping or trapping, extracranial to intracranial bypass followed by proximal endovascular parent occlusion, or endovascular techniques alone. We have taken this approach in 56 giant aneurysms in 54 patients. In considering each case, the patient's age, overall medical condition, and the exact size and location of the aneurysm was taken into account prior to deciding on the final treatment plan.

Presenting signs and symptoms were compressive (cranial nerve or cerebral tissue) in 27 patients (50%). Subarachnoid hemorrhage was the presenting sign in 14 patients (26%), and headache the presenting sign in 10 patients (18%). Seizures occurred in 3 patients (6%). Most lesions occurred in the internal carotid artery (32 aneurysms) with 7 occurring on the middle cerebral artery, 6 on the anterior cerebral artery or anterior communicating artery, and 8 in the vertebrobasilar circulation. Three aneurysms occurred on the posterior cerebral artery distally.

Of the 54 patients managed, 21 underwent direct surgical clipping or trapping (39%). Eight patients (15%) had planned extracranial-intracranial bypass procedures with proximal balloon occlusion. Endovascular balloon occlusion was used in 13 patients (24%). In these patients, 10 procedures were performed for proximal vessel occlusion. Twelve patients (22%) had detachable coil therapy with the recently available GDC (Guglielmi detachable coil) system.

Using a combined modality approach, excellent or good results were obtained in 48 patients (89%). A fair outcome (defined as having neurological deficit, able to live at home but unable to return to work or previous lifestyle) occurred in 3 patients (5%), and a poor outcome occurred in 1 patient (2%). There were 2 deaths in the series (4%).

With a variety of techniques available to treat giant intracranial aneurysms, it seems appropriate to try to tailor the management of each patient. As newer techniques are developed, these must be incorporated into the standard management of giant aneurysms. Despite advances in surgical and endovascular techniques, giant aneurysms still carry a significant risk in terms of treatment, and in some patients, careful followup without intervention is the best option. By using a multimodality approach in the treatment of these lesions, it is hoped that morbidity and mortality will be minimized.

Figure 1. Left. CT scan of a 64 year old woman with a giant internal carotid artery aneurysm. A large round density demonstrates calcification of the wall of the aneurysm with thrombus within the lesion.

Right. Coronal MRI scan of the patient shown in Figure A, demonstrating thrombus within the lesion and a small area of the aneurysm which still fills with blood.

Figure 2. Left. Lateral angiogram of the patient demonstrated in Figure 1. The internal carotid artery injection demonstrates filling of the aneurysm. The lesion was deemed to be untreatable with direct surgical attack, and for that reason a bypass graft was placed.

Right. Lateral angiogram of the patient in Figure 2A after placement of an extracranial-to-intracranial bypass graft and occlusion of the internal carotid artery using intravascular balloons proximal to the aneurysm. Excellent filling of the middle cerebral artery was demonstrated, and the patient had no neurologic deficit.

Figure 3. Left. Coronal MRI study of a patient who presented with visual field cut and pituitary dysfunction. The patient was found to have a partially thrombosed giant aneurysm.

Right. Axial MRI study of the patient seen in Figure 3A. The hyperintense region of the lesion is the area which remains patent. The remainder of the lesion was thrombosed.

Figure 4. Left. AP view of the internal carotid angiogram demonstrating a giant aneurysm with a small neck. The lesion was approachable surgically and could be clipped without difficulty.

Right. Postoperative AP angiogram demonstrating complete obliteration of the aneurysm at the neck with an aneurysm clip. The aneurysm could then be opened surgically and the thrombus removed, alleviating the patient's symptoms of optic chiasm compression and endocrine abnormality.

Other Information sources on giant intracranial aneurysms:

Ojemann RG, Ogilvy CS, Heros RC, Crowell RM, eds. Surgical Management of Cerebrovascular Disease, Third edition. Williams & Wilkins, Baltimore, in press.

Disclaimer About Medical Information: The information and reference materials contained herein is intended solely for the information of the reader. It should not be used for treatment purposes, but rather for discussion with the patient's own physician. All visitors to this and associated sites from the Neurosurgical Service at MGH agree to read and abide by the the complete terms of legal agreement found at the Neurosurgery "disclaimer & legal agreement." See also: the MGH Disclaimer, the MGH Privacy Policy, and the MGH Interactive Program Disclaimer - Copyright 2006.
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